Extractive distillation of alcohols obtained from olefins



22, 1953 w. M. DRoUT, JR

EXTRACTIVE DISTILLATION OF ALCOHOLS OBTAINED FROM OLEFINS Filed Dec?.3l, 1948 4J-Lillian: h2. @rout,Jrr Inventor Patented Dec. 22, 1953EXTRACTIV E DISTILLATION OF ALCOHOLS OBTAINED FROM OLEFINS William M.Drout, Jr., Linden, N. J., assignor to Standard Oil Development Company,a corporation of Delaware Application December 31, 1948, Serial No.68,453

4 Claims.

This application is a continuation-in-part of U. S. patent applicationSerial No. 24,626 filed May 1, 1948, now Patent 2,638,440, granted Mayl2, 1953.

This invention relates to the purification of organic liquids andvapors. More specifically the invention relates to an improvedextractive distillation process for the puriiication of organic liquidsand vapors. In particular the invention is concerned with thepurication. ci organic liquids by extractive distillation in which thedistillation is carried out without the conventional external reflux sothat vapors are removed from the distillation column Without further-condensation above the point of entry of the extractiva distillationsolvent.

The invention has wide application and may be employed in extractivedistillation operations to accomplish among others the followingseparations: an alcohol from impurities boiling over a widerange; one ormore alcoholsV from other close-boiling alcohols; alcohols from otheroxygenated compounds such as ketoncs, aldehydes, esters, etc.; waterfrom organic compounds such as alcohols, ketones, etc.; hydrocarbonsfrom their isomers such as nieta xylene from para Kyle-ne; paraiiinsfrom oleiins, oleiins from dioleins; etc. In each of the above mentioned.applications the appropriate solvent suitable for the separation, e.g., Water, aqueous salt solutions, acetone, hydrocarbon oils, aromaticothers, etc., is employed during the extractive distillation process.However the process or this invention is applicable to extractivedistillations of all types, i. e., regardless of the separation beingmade or the particular solvent employed.

It is an object of this invention therefore to provide a process forthe. purification of organic liquids by an improved Vextractivadistillation process in which the customary external reiiux is omittedso that vapors are removed from the distillation column Without furthercondensation above the point of entry oi the extractive distillationsolvent.

It is another object of this invention to provide a novel and improvedprocess for the purification of alcohols, particularly alcohols of 2 to5 carbon atoms produced by the reaction of mono-oleiins, by removingtherefrom impurities both watersoluble and water-insoluble andodorproducing contaminants.

These and other objects of the invention are accomplished by subjectingthe organic liquid to extractive distillation in a distillation zoneinthe presence-oi an extractive distillation solvent the nature, conditionand amounts of which are determined by the purification being effected,and carrying out the distillation in the absence of conventionalexternal reflux so that vapors are removed from the distillation Zone.Without further condensation above the point of entry of the solvent. v

Although the invention is applicable to the seperations listed aboveamong others, it is particularly applicable to the purification ofaliphatic alcohols especially those of 2 to 5 carbon atoms per moleculeprepared from mono-olelins either by acid-catalysed hydration or by theso-called 1 oxo-synthesis of an olelin with carbon monoxide followed byhydrogenation.

By the catalyzed hydration of oleiins is meant those processes in whichmono-olens are hydrated in the presence of a catalyst, including thewell known acidV catalyzed processes wherein mono-oleiins are hydratedinthe presence of polybasic mineral acid-acting acids such as sulfurieacid, phosphoric acid, and benzenesulfonic acid; and also thoseprocesses, sometimes .called direct hydration processes, inwhich theoleiin is hydrated in the presence of solid catalysts such as phosphoricacid, phosphoric acid-tungsten ox ide, etc. or dilute aqueous acids,such as sulfuric acid or phosphoric acid etc.

This invention will be described in its application to the puriiicationof crude alcohols produced from mono-oleiins but it is to beunderstood'that the invention is notv limited thereto since it has equalapplication to other extractive distillations regardless of theseparations being eliected.

By operating according to the terms of this'invention high yields oihighly refined alcohol ofr excellent odor characteristics can beproduced for use in specialized industries, such as the cosmetio,perfume, drug, biological and vitamin industries. I-leretoiora` suchalcohols were obtained only in very poor yields and athigh costvby frepeated refractionations of partially refined alcohols.

It is well known that alcohols produced'by the sulfuric acid hydrationof olelin hydrocarbons.Vv possess a distinct and apparent foreign odor,y

taking overhead all or substantially all of the impurities contained inthe crude alcohol, namely, the ethers, ketones, other alcohols, lighthydrocarbons some of which impurities boil' as flow as C., and even allor a substantial portion of the` high Iboiling polymer oils. Thedistillation tower is operated without the conventional external refluxso that vapors are removed overhead without further condensation abovethe point of entry of the extractive distillation solvent. theimpurities taken overheadrboil normally at a temperature above theboiling point of the alcohol which is being purified, e. g. the polymeroils which'boil as high as 250 C. to 300 C. Additional polymer oilimpurity, particularly a portion of the higher boiling fractionsthereof, concentrates in the column at a point near the alcohol feedplate upon contact of the crude alcohol feed with reflux water. Thisconcentration of polymer oil occurs near the alcohol feed plate. Astream containing the polymer concentrate is removed from thedistillation column at. this point and the polymer removed therefrom bydecantation. The dilute alcohol phase is returned toV the column at apoint about one plate below the withdrawal point. In this mannerpractically all the odor-producing contaminants Vare removed from thealcohol. The dilute aqueous alcoholY product obtained as bottoms fromthe distillation zone and containing between6599 mol per cent water isled to a concentrating column, wherein the desired alcohol isconcentrated and recovered in high yields. The product is far superiorinf odor to any alcohol obtained by any cation methods known to the art.,Y i If desired, the crude aqueous alcohol may bek treated prior to theextractive distillation step, with additional amounts of water tokthrOW'out of solution the bulk of the polymer'oil, particu-'- larly thehigher boiling constituents of the polymeroil.'

It has been found that 95 volume per cent of the alcohol present in acrude aqueous isopropyl alcohol from thehydration of propylene havingyof the puri-' the following composition, can be recovered as highpurity, excellent odor alcohoLby concentrating the weak `alcoholrecovered as bottcmsfrom a 45 plate water extractive distillationcolumn:

65 volume percent isopropanol.

` 1.4 volume per cent propyl .oil (based on alcohol content). 0.2 volumeper cent acetone (based on alcohol content). v

5.1,vo1ume per cent isopropanol ether (based on (i alcohol content). lBalance-Water and other impurities.r

By operating the 45 plate extractive distillation column at a 2:1 reduxto heads ratio with the alcohol feed rate (alcohol feed to the 30thplate 1v and the water feed rate (water feed to the 45 plate) adjustedso that a 23.5 volume per cent:

alcohol was drawn off at the bottom of the column, it was possible toremove the following proportions of the feed components from the alcoholin the overhead from the column:

69.7 volume per cent pl'Opyl oil.

100 volume per cent acetone. Y

100 volume per cent isopropyl ether.

5.2 volume per cent isopropyl alcohol.

Although the overhead from the above distilla' tion contained 5.2 volumeper cent of the isopropyl alcohol fed to the column, it is possible byyemploying optimum distillation conditions to hold Many of the alcoholcontent of the overhead to a much smaller amount, say 1 volume per centor less. The weak 23.5 volume per cent aqueous alcohol recovered fromthe extractive distillation columnV was concentrated in a 40 plate batchdistillation column. i The accompanying drawing represents a flow planin elevation of one process and accompanying apparatus for carrying outthis invention.

Referring to the drawing, numeral 2 represents an extractivedistillation tower, such as a plate column, to which crude isopropylalcohol or partially refined isopropyl alcohol containing 0 to v volumeDer cent water is fed via line I. The feed line is located at a pointpreferably above the midsection of the distillation column, for example,at about the 30th plate in a 45 plate tower. Water is fed to the towerin considerable amounts through line 3. The water is fed to the top ornear the top of the tower but'always above the alcohol feed plate. Toobtain the desired separation of the impurities from the alcohol, themixture is subjected to a continuous fractional distil-V lation incolumn 2. The water introduced in suinciently large quantity at theupper part of the tower effectively modifies the relative volatilitiesof the organic compounds being separated, and distillation of anextremely large part of the impurities from the alcohol is effected. Thetemof the internal liquid reflux under equilibriumv boiling conditionsat the point of introduction.Y

The preheated alcohol feed stream Vmay be liquid, partially vaporized orcompletely vaporized when introduced into the fractionation column.Vapors of the organic compounds introduced as a feed stream passupwardly through the distillation zone in contact with descendinginternal liquid reux under equilibrium reboiling and re fluxingconditions. Due to the fact that water, considerably in excess of theamount of water dirtilled, is introduced to mix with thecondensate nearthe top of the distillationzone, the water AVVconcentration in vtheinternal liquid reflux at the top ofthe distillation zone is higher thanthe water concentration in vapors passing up through the zone. Excellentresults have been obtained by operating the column with pure waterreflux without the return of an external condensate. Contrastedtherewith in'normal rectification of alcohols from an aqueous feed,thewater concentration diminishes rapidly toward the limiting waterconcentration of the aqueous azeotropes in the vapors ascending thedistillation column.

The quantity of water required to be introduced continuously at theupper part of the distillation zone for accomplishing the desiredseparation of the impurities from the alcoholis considerably 'greaterthan the quantity of condensate with which it becomes homogenecuslymixed on each plate in order to make the water concentration of theinternal refluxsubstantially above a critical minimum in the range of'Z0-99.9y mol per cent.'

With adequaterwater concentration.V in the internalrefluxfor-f-,elfectine the. separation, the SQQIIQI; tog-.be isolated inthe;aqueqtlsnbottumsis dissolved the aqueous internal refluxv f that'reaches the .bottom-- of I the distillaticn column. Excellent.- quality'isonropylsalcohol was ontained-v by adjusting the alcohol to water feedratiqso; that 15.251volume percent alcoholwas-obta-ined thel bottom of'`thedistillationv column.

Returning to the drawing; impuritiescon-tainedl inthe-1isopropyL-alcohcl.- namely,-isonropvlfether, acetone, a substantial ipart i. of l the prfopylr` oil,v Water, etc. are-'removed overhead.'via` line 4; con-- densed in condenser-` 5 fandremoved from the sys-1-tem vial line 'l. Par-tf of the condensate-may be re. uxed tothetopfofthecolumnsvia lined. :How-l ever, it;z has been foundftl'iatla:furtherimprovesA ment, the quality` of alcohol canbe obtained withoutlossv of` alcohol yield; by .operating the-exsi tractivepdistillationfcolumn without the convene. tional reilux-Yso that. vaporsl-varefremovedfiloni, the; column.. without further` condensation::aboveethe: point,vof'entr'y of the extractivadistillation 5.0i` vent.Byoperating-without external; reflux;from thecondenser, the extent ofreflux: the .-towelal isv'controlled only by: the condition andarnountofv the; solvent f entering the tower through- -line. Thus the solventitself acts -as apartial condenser, when. the temperature` of thesolvent. is .Y properly controlled. OmittingI theeexternal reuxfitl.has.- been foundl that there willastill be aufeffectivere` flux; in thetower becausef-atf the point of intro ductionr of the solvent into theVtower-no equilibriumf, exists between` the; vaporseandfthefsoluent .l Asthe solvent free off-alcohol descends-a1 fewv plates down the tower--itspicks unalcohol untill-it reaches a steady state:` condition.'Ihetresult is the same as if reiuxing y'ofathe desir-ed puresalfcol-iolhadbeenfachieved Ithasfbeen-foundwthat thereliuxf ratio can be;yeffectively eontrolledfbal tween` land. 10:1 byomittinggthe;conventionahexternal reflux and.` 'introducing` thepextractiuedistillation solventinto-the tower: ata-1 tempera-- ture somewhat below its--boilingrpointfsay in thecase of waterata-temperaturef o f120.95?, G preferably {S5-'95C. If anextremely pure-product is desired, e.V g.,` practically 100%pure alcohol,4 it may be attained at the'expenseoffaesmall loss ofthe-alcohol overheadwith thedmpuritiesfbeing removed. To accomplishVthis the solventsis iri-K troducedinto the tower-atafcclderftemperature,- i. e.,- ataI temperature nearer the lowes level?,ot the range expressedandfno externalgrefluxiseemf. ployed. Byoperatingein this mannerfonefavoids having 'any of theimpurites broughtbacio-zdown into the tower'over the amount' condensedon--any one platein ther-tower particularlyr'between the; feedplatefand the point ofintroductiomof-.the solvent.

Additional high boilingpolymer oil has. been foundtoconcentrate as--aseparatev phasein .the column at a point near; the alcohol feedrplatewhen the feed is mixedzwith the aqueousre.- flux stream. A sidestreamcontaining. this polymer oil concentrate is removedyfrom thecolumnandthe polymer oil isseparatedby continuous decantation, thus minimizingforvirtually eliminating polymerffoil from vthe concentrating column. Thissidestream is removedfrom/the column atga pointbelow thecrudealcohoLfeed plate, but preferably ata point;inlinediately.be-Vlow'the alcohol feed platel- To thisgendfastrcam can :be removed fromtower 2v'via-line 24- and senirzto decanter '25. This stream; iswithdrawn at.a-fpoint near the alcoholfeed mateurslightly l'ielowthe`alcohol feedyplate,y In-thefdecanter the: streamf separates: into anupper. polymer oil phase `Vwhich. is discarded,4 andV a lower aqueousalcohol streamf 26 freedof polymer oil., The

latter is vreturnedtoY the tower via line 2l ata point aboutra platebelow the withdrawal point;

Bottoms lfrom theA tower 2, consistingchiey of aq ueous alcohol of aboutV10--40 volumaper c ent, preferably 15-25 volume per centis removed vialinel` 8k and introduced to concentrating-.colf umnflZ.V Part of theaqueous bottoms: iswithdrawnl fromrline 8 via line Inf-and senttoreboiler 9 for heating by indirect or direct heat exchange withfaheating medium, such as live steam,`and returned via line It tothedistillation column. In .column l2 `theaqueous alcoholV is concentratedto the desired levelA up to,y the 91,3 volume per cent, isopropylalcohol-water azeotrope, whichgls removed -as a sidestream nearA thetop. of;` the column vrvialine I l. Thev remaining propyl'oll; if any,contained iny the` aqueous -alcoholisVre-l movedfrom. the. concentratingcolumn-in a- Sidestream t8 at a point. aboutthree plates :above thefeedplate. Someremaining traces oflight material,..ifrany, and. alcohol areremoved over-f head via rline i3, condensed in condenser M. and removedfrom the system via line I6. If desired, this overhead may be recycledtothe extractiva distillation zone. Part ofv the condensate .may be reuxedto thetop of, the columnvia line I5. Bottoms from the concentratingvcolumn consisting. substantially of. Water are removed via. lineV i9 andmay be recycled in whole `or! in part to the extractiva distillationtower.2-.via water supply line 3. Excess water may bere--V moved fromthe systemvia line 23. A. portion ofthev aqueous bottoms may bewithdrayvnlvia line 20 andfsent to-reboiler 2l for heatingby indirect ordirect heat exchange with Ya heating medium such. as live steam andrecycled to column I2 vial line 22. Although the dilute aque,-V

ous alcohol solution from the distillationzone has beendescribedasconcentrated by fractional distil1ationother means of concentrationmay beemplo'yedsuch as solvent extraction.

Irithe separation ofY impurities from,isopro. panolproduced by theacidcatalyzed hydra-.v tioni of` propylene, essentially no Y satisfactoryseparation is. effected if the internal reflux contains less than '70mol per cent water. For obtaining satisfactory results on apractical-scale theipreferred range isi-99 mol per cent -Water in theinternal reux.

VUndersteady conditions in the extractiv'efdistillation zone, theinternal reflux, having/adequate-water:concentration for accomplishingthe separation of the wide-boiling'impurities, tends to have a nearlyconstant water concentration ina-.preferably homogeneous liquid phaserateach plate; andthe high water concentration'is ap:- proximately uniforminv the internal reflux-be.- low the alcohol feed plate. This internalreflux in flowing from the topto the bottomof tower becomes richerv inthe alcohol while:.the other impurities of the feed becomel distilledvoverhead.

In the distillation.. process the mol percent water in the totaloverhead from the extractiva distillation column will vary with theoperating conditions and with the nature of the impurities rejectedoverhead. The aqueous 'bottoms' re# moved from the extractivadistillation zone will contain approximately r70-99'molper cent. water.

The overhead-'from the' extractive distillation` zone' uponcondensation-k and cooling1frequently, separates into two phases;` anaqueous phasefandl an organic phase. An Engler distillation oi a typicalorganic phase, resulting from the purification of isopropanol revealsthat the initial boiling point lies between 40-50 C., and the nalboiling point is approximately 250 C., indicating that there isconsiderable high` boiling ma.- terial contained in the overhead.

Without attempting to explain the mechanism by which the desiredseparation occurs in the distillation column, it can be said that theprocess is one ,of vapor-liquid extraction in which the vapors contain agreater relative concentration of the impurities than under the normalfractionation conditions in the absence of the considerable amount ofwater internal reflux. It is evident from the results obtained that theWater employed within the limits specied, increases the effective vaporpressures of the impurities relative to the vapor pressure of thealcohol being purified, thus allowing the impurities to pass overheadfrom the distillation zone. Although it is preferable not to have anyplates in the tower above the water feed plate, it is possible to carryout the separation with a limited number of plates above the water feedplate. However, this number should be held toa minimum.

Although the invention has been described employing pure water in thedistillation process, it is also permissible in the purification ofalcohols to use water containing a small amount of salts, such as sodiumacetate, or acid, such as sulfuric acid or even caustic, such as sodiumhydroxide.

Although the invention has been illustrated by the purification ofisopropanol, it is equally applicable to the puriiication of otheralcohols of 2 to 5 carbon atoms per molecule resulting from the reactionof mono-olelns, such as ethanol, tertiary butanol,` secondary butanol,the secondary amyl alcohols, and tertiary amyl alcohol. In this regardthe impurities are removed in a manner similar to that described for theisopropanol system. The following are approximate typical compositionsof some of the crude aqueous alcohols which may be treated according tothis purification process;

Crude ethyl alcohol 80-85 weight per cent ethyl alcohol.

9-14 weight per cent ethyl ether.

0.2-0.8 weight per cent hydrocarbons (B. l?.

2.5-5 weight per cent colloidal carbon.

Crude secondary butyl alcohol 7 5 weight per cent butyl alcohol.

5 weight per cent secondary butyl ether. 4 weight per centl polymeroils.

Balance water and other impurities.

Crude secondary amyl alcohols volume per cent sec-amyl alcohol. 20volume per cent hydrocarbons. 5-10 volume per cent sec-butyl alcohol.2-5 volume per cent tertiary amyl alcohol. 5-10 volume per cent water.2-3 volume per cent others, e. g. sec-amyl, sec'- butyl and mixedothers. 2-5 volume per cent higher alcohols, e. g. hexyl alcohols. 1-2Volume per cent ketones, e. g. diethyl ketone or methyl propyl ketone.

As previously mentioned, the operating conditions will vary with thenature of the alcohol being puried. In this respect the amount of wateradded to the distillation column is important. When purifying secondarybutanol, it has been found that sufiicient water should be added to thedistillation column to maintain a composition ofv -99.9 mol per centwater in the liquid phase in the column. For secondary amyl alcoholssu'icient water should be added to main. tain a composition of 97.5 to99.9 mol per cent water in the liquid phase in the column.

Laboratory data obtained with a ll5-plate column, withwater being fed tothe 45th plate and crude isopropanol to the 30th plate, are given inTable I. Conrmatory data obtained with a30- plate commercialdistillation column, with water being fedto the 29th plate and crudeisopropanol to the 23rd plate, are given in Table II. The results showby comparison the advantages of operating without theconventional'external reflux.

TABLE I 46 plate laboratory column IPOH Optical density of Temper-Percent concenproduct l R x Mol perature of organic tratlon Percent et-)cent HnO H2O material (volume IPOH ra l added added ejected percent)yield C.) in heads in column 2,250 A 2,700 A bottoms 90. 9 93-95 14. 427. 5 90. 5 0. 299 0. 107 93. 5 93-95 14. 1 22. l 89. 3 0. 227 0. 05091. 5 93-95 16. 1 28. 5 90. 6 0. 206 0. 023 89. 0 93-95 13. 8 3l. 8 92.1 0. 193 0. 023 88. 6 9395 l2. 4 33. 3 91. 2 0. 149 0. 060

1 Same as in Table II.

T BLE II 30 plate commercial distillation column IP OH Optical densityof Temper- Percent concenproduct 1 Reex Mol perature of organic trationPercent ratio cent H2O H2O material (volume IPOH added added ejectedpercent) yield C.) in heads in column 2,250 A 2,7001A" bottoms 1 Incomparison with distilled water. Odor ci alcohol increases withincreasing optical density at these wavelengths.

ill

n addition to thepurication 'of aliphatic alcohols as outlined, the

invention is also applicable to the following extractive distillation"processes:

Object of distillation Extraotive distillation solvent Separation ofclose-boiling alcohols, IPOH (overhead) :froi'i (overhead) from n-BuOH(bottoms), etc.

Separation of alcohols (bottoms) from non-alcoholic oxygenated H(E10-99.9 mol percent, preferably 70-,99 mol percent), higher alcohols,sulfolane, phenol, vglycols, .glycol ethers, esters, ether-esters, hydrooarbons, salts, etc.

-HzO (50-09-9 mol percent,

preferably 85-99 mol percomponnds (overhead). cent). Dehydration ofalcohols Water immiscible alcohols,

.gasolina etc.

-Do. Hydrotropic salts, e. g. sullonatesyetc.

Acetone, f urural, etc.

"The process is applicable Whether the Vdesired component is beingrecovered overheadfromthe extiactive distillation tower 'or whether'itis recovered as a solution in the solvent at thel bottom ofthe tower,,since the purpose of the solvent is tofiniprove the `relativevolatility-(alpha) of the componentseregardless of the-directionin whichthey ver@ separated.

What claimedl is:

1. The method lof renn-ing a crude (I2-C5 aliphaticfalcohol producedyby-reaetionof a mono- ,olefinY said crude 'alcohol containingcontaminants'lowereboiling andA higher -boiling than the alcohol. .some.of-saidV higher boiling impurities beingvvaporized with Water under`distillation conditions'hereinafter mentioned and some .of-saidhigherboiling-'impurities being non-vaporizable u 4 der-said-V conditionawhichcomprises introducing the-crudezalcohol to a--fractional distiljlationLzone f at anl intermediate l point thereof,` introducingsulicient4vvater at a` temperature `(01320-959 C. ,to the;l fractionaldistillationzone .at apoint substantially above the crude alcohol feedpoint to maintain an internal "liquid "l to 299(.9111'0'1Y ,per Icentwaterj -belowft'he *point of "addition j of the watery* di's'tilling"from said crude alcohol a"vaporous mix-mire comprising water, thealower" -boilingl-in'rpurities yand the Vhighery boiling v'impuritiesfwhich Y vaporizewith Water under the distillation :conditions whereilithe vaporous mixture --flo-Ws"-countercurrentto 'the internal aqueous-liq'uid reflux,- `and" removing said' I vaporous mixture -oxerheadffii-'omi the fractional distillation zone; -reniovingfa ybottomsproduct from the distillation zone-f containing Water,A alcohol', ian'd-.the'l'higher boiling i impunitiesff-whiclido A*not vaporize 'vv'ithrWater; :saidfdistilllation' being-l1 conducted l :Without returrn-glctothe 2' distillationzone fthe thusdistilledl vcorn-ponentsoftheloverheadidistillate.

v2. Their method fof yclaim 1.1m which the crude alcohol is ethanol.:and in which the water: conltent lof "the internal-,liquidf refluxmaintained inltheran'gelof to' 99 mol-percent.

'3.5Them'ethod of claim 12in Ewhichftlie'alcohol iisopropanol .andcinwhich vrthe :Water cor-itentof the .internal liquidireflux is maintained`at'i70 to-99"m`ol per Icent.

4. Theimethod of iiclaim 1 in which-the-alcohol issecondary butanol' andin which'the water content of the internal liquid reuxfzismaintained -atltoV 99.9 mol per cent.-

Wl" LLIAMV4 11ML' DROU'I'-, fJnL References .t'Jitd-"inM .the `file ofthis patent UNITED STATES PATENTS 2,080,111 VBump MayI 11,1 19372,179,991 Bright et al Nov. 14, 1939 2,198,651 Bludworth Apll' 30, 19402,215,915 Cope et al Sept. 24, 1940 2,283,911 Brant et al -May 26,' 19422,290,442 Metzl July 21, 1942 2,290,636 Deanesly lJuly 21, 19422,321,748 Hopkins etal June-'15,4943 2,379,110 Souders June`26,19452,551,593 Gilliland et al *May-'8,l1951

1. THE METHOD OF REFINING A CRUDE C2-C5 ALIPHATIC ALCOHOL PRODUCED BYREACTION OF A MONOOLEFIN, SAID CRUDE ALCOHOL CONTAINING CONTAMINANTSLOWER BOILING AND HIGHER BOILING THAN THE ALCOHOL, SOME OF SAID HIGHERBOILING IMPURITIES BEING VAPORIZED WITH WATER UNDER DISTILLATIONCONDITIONS HEREINAFTER MENTIONED AND SOME OF SAID HIGHER BOILINGIMPURITIES BEING NON-VAPORIZABLE UNDER SAID CONDITIONS, WHICH COMPRISESINTRODUCING THE CRUDE ALCOHOL TO A FRACTIONAL DISTILLATION ZONE AT ANINTERMEDIATE POINT THEREOF, INTRODUCING SUFFICIENT WATER AT ATEMPERATURE OF 20-95* C. TO FRACTIONAL DISTILLATION ZONE AT A POINTSUBSTANTIALLY ABOVE THE CRUDE ALCOHOL FEED POINT TO MAINTAIN AN INTERNALLIQUID REFLUX HAVING A WATER CONTENT IN THE RANGE OF 65 TO 99.9 MOL PERCENT WATER BELOW THE POINT OF ADDITION OF THE WATER, DISTILLING FROMSAID CRUDE ALCOHOL A VAPOROUS MIXTURE COMPRISING WATER, THE LOWERBOILING IMPURITIES AND THE HIGHER BOILING IMPURITIES WHICH VAPORIZE WITHWATER UNDER THE DISTILLATION CONDITIONS WHEREIN